Seasonal patterns of root production of Japanese oak seedlings and dwarf bamboo grown in rhizoboxes

Abstract

We separately examined the temporal patterns of root production by Japanese oak (Quercus crispula) and dwarf bamboo (Sasa veitchii), which is a major understory species in cool temperate forests. We grew Japanese oak seedlings and Sasa stocks (i.e., the rhizome and connected culms) in organic‐free sand in rhizoboxes and then scanned roots that were visible through the sides of the rhizoboxes to measure the length of each root in images. Japanese oak root production peaked in July, but Sasa root production peaked in both July and October. Soil temperature was highly correlated with root production of Japanese oak, but less so with Sasa root. Leaves of Sasa expanded in late summer, and the photosynthetic rate of Sasa was highest in September, suggesting that the aboveground phenology influences the extensive root production of Sasa in October due to the supply of carbohydrate. These results demonstrate different temporal patterns of root production by Japanese oak seedlings and understory species (Sasa), even under similar environmental conditions.

Keywords:

• Root production
• leaf phenology
• Japanese oak
• rhizobox
• Sasa
• understory vegetation

Acknowledgments

We thank the staff of the Kitashirakawa Experimental Station of the FSERC, Kyoto University, for providing technical support and meteorological data. We also thank Ms Momoko Sakai, Dr Keitaro Fukushima (Kyoto University) for helping with the measurements, Dr Naoko Tokuchi (Kyoto University), Dr Daniel Epron (Nancy University), members of Field Science Center for Northern Biosphere, Hokkaido University for valuable comments, and Dr Shozo Shibata (Kyoto University) for helpful comments concerning cultivation of Sasa bamboo. This research was supported in part by a Japanese Society for Root Research (Karizumi) Young Researcher Travel Award and a Grant‐in‐Aid for Young Scientists (No. 20780116) from Japan Society for the Promotion of Science.